¹M. J. Burchell, ¹K. H. McDermott, ¹M. C. Price,¹L. J. Yolland

¹ Centre for Astrophysics and Planetary Science, School of Physical Sciences, Ingram Building, University of Kent, Canterbury, Kent CT2 7NH, UK

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Reference
Burchell MJ, McDermott KH, Price MC, Yolland LJ (2014) Survival of fossils under extreme shocks induced by hypervelocity Impacts. Philosphical Transactions of the Royal Society A, 372: 2023

Link to Article [doi: 10.1098/rsta.2013.0190]

¹ M.A. van Zuilen,¹ P. Philippot,² M.J. Whitehouse,^3,4 A. Lepland

¹ Géobiosphère Actuelle & Primitive, Institut de Physique du Globe de Paris, Sorbonne Paris Cité, UnivParis Diderot, UMR 7154 CNRS, F-75005 Paris, France
² Swedish Museum of Natural History, Box 50007, SE104-05 Stockholm, Sweden
³ Geological Survey of Norway, Leiv Eirikssons vei 39, 7491 Trondheim, Norway
⁴ Tallinn University of Technology, Institute of Geology, 19086 Tallinn, Estonia

Theoretical and experimental studies have shown that atmospheric SO2 isotopologue self-shielding effects in the 190-220 nm region of the solar spectrum are the likely cause for mass independent fractionation of sulfur isotopes (S-MIF). The main products of this photochemical reaction – SO3 and S0 – typically define a compositional array of ca. Δ33S/δ34S = 0.06-0.14. This is at odds with the generally observed trend in Archean sulfides, which broadly defines an array of ca. Δ33S/δ34S = 0.9. Various explanations have been proposed, including a diminution of δ34S caused by chemical and biogenic mass-dependent fractionation of sulfur isotopes (S-MDF), mixing with photolytic products produced during felsic volcanic events, or partial blocking of the low-wavelength part of the spectrum due to the presence of reduced atmospheric gases or an organic haze. Early in Earth history large meteorite impacts would have ejected dust and gas clouds into the atmosphere that shielded solar radiation and affected global climate. It is thus likely that at certain time intervals of high meteorite flux the atmosphere was significantly perturbed, having an effect on atmospheric photochemistry and possibly leaving anomalous sulfur isotopic signatures in the rock record. Here we describe the sulfur isotopic signatures in sulfides of spherule beds S2, S3 and S4 of the Barberton Greenstone Belt, South Africa. In particular, in spherule bed S3 – and to a lesser extent S4 – a trend of ca. Δ33S/δ34S = 0.23 is observed that closely follows the expected trend for SO2-photolysis in the 190-220 nm spectral range. This suggests that an impact dust cloud (deposited as spherule beds), which sampled the higher region of the atmosphere, specifically incorporated products of SO2 photolysis in the 190-220 nm range, and blocked photochemical reactions at higher wavelengths (250-330 nm band). By implication, the generally observed Archaean trend appears to be the result of mixing of different MIF-S sources arising from a variety of photochemical reactions that took place in the lower part of the atmosphere.

Reference
van Zuilen P, Philippot P, Whitehouse MJ, Lepland A (2014) Sulfur Isotope Mass-Independent Fractionation in Impact Deposits of the 3.2 Billion-year-old Mapepe Formation, Barberton Greenstone Belt, South Africa. Geochimica et Cosmochimica Acta (in Press).

Link to Article [DOI: 10.1016/j.gca.2014.07.018]

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¹S. Marchi, ¹W. F. Bottke, ^2,6L. T. Elkins-Tanton, ³M. Bierhaus, ³K. Wuennemann, ⁴A. Morbidelli ⁵D. A. Kring

¹Southwest Research Institute, Boulder, Colorado 80302, USA
²Carnegie Institution for Science, Washington DC 20015, USA
³Museum für Naturkunde, Berlin 10115, Germany
⁴Observatoire de la Côte d’Azur, Nice 06304, France A. Morbidelli
⁵Universities Space Research Association, Lunar and Planetary Institute, Houston, Texas 77058, USA
⁶Present address: School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287, USA

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Reference
Marchi S, Bottke WF, Elkins-Tanton LT, Bierhaus M, Wünnemann K., Morbidelli A, Kring DA (2014) Widespread mixing and burial of Earth’s Hadean crust by asteroid impacts
Nature 511, 578–582

Link to Article [doi:10.1038/nature13539]

^1,2,3 Camille Cartier,^1,2,3Tahar Hammouda, ^1,2,3 Maud Boyet,^1,2,3 Mohamed Ali Bouhifd, ^1,2,3 Jean-Luc Devidal

¹ Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, BP 10448, F-63000 Clermont-Ferrand, France
² CNRS, UMR 6524, LMV, F-63038 Clermont-Ferrand, France
³ IRD, R 163, LMV, F-63038 Clermont-Ferrand, France

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Reference
Cartier C, Hammouda T, Boyet M, Bouhifd MA, DevidalJ-L (2014) Redox control of the fractionation of niobium and tantalum during planetary accretion and core formation. Nature Geoscience 7, 573–576

Link to Articel [doi:10.1038/ngeo2195]

¹E. Asphaug, ^1,2A. Reufer

¹ School of Earth and Space Exploration, Arizona State University, PO Box 876004, Tempe, Arizona 85287, USA
²Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland

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Reference
Asphaug E, Reufer A (2014) Mercury and other iron-rich planetary bodies as relics of inefficient accretion. Nature Geoscience 7, 564–568

Link to Article [doi:10.1038/ngeo2189]

^1,2Masaaki Miyahara, ^1,3Eiji Ohtani, ⁴Akira Yamaguchi, ^1,4Shin Ozawa, ^1,5Takeshi Sakaia, ⁶Naohisa Hirao

¹ Institute of Mineralogy, Petrology and Economic Geology, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan;
² Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan;
³ V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russia;
⁴ National Institute of Polar Research, Tokyo 190-8518, Japan;
⁵ Geodynamics Research Center, Ehime University, Matsuyama 790-8577, Japan; and
⁶ Japan Synchrotron Radiation Research Institute, Hyogo 679-5198, Japan

Howardite–eucrite–diogenite meteorites (HEDs) probably originated from the asteroid 4 Vesta. We investigated one eucrite, Béréba, to clarify a dynamic event that occurred on 4 Vesta using a shock-induced high-pressure polymorph. We discovered high-pressure polymorphs of silica, coesite, and stishovite originating from quartz and/or cristobalite in and around the shock-melt veins of Béréba. Lamellar stishovite formed in silica grains through a solid-state phase transition. A network-like rupture was formed and melting took place along the rupture in the silica grains. Nanosized granular coesite grains crystallized from the silica melt. Based on shock-induced high-pressure polymorphs, the estimated shock-pressure condition ranged from ∼8 to ∼13 GPa. Considering radiometric ages and shock features, the dynamic event that led to the formation of coesite and stishovite occurred ca. 4.1 Ga ago, which corresponds to the late heavy bombardment period (ca. 3.8–4.1 Ga), deduced from the lunar cataclysm. There are two giant impact basins around the south pole of 4 Vesta. Although the origin of HEDs is thought to be related to dynamic events that formed the basins ca. 1.0 Ga ago, our findings are at variance with that idea.

Reference
Miyahara M, Ohtani E, Yamaguchi A, Ozawa S, Sakaia T, Hirao N (2014) Discovery of coesite and stishovite in eucrite. Proceedings of the National Academy of Sciences 111, 30.

Link to Article [doi: 10.1073/pnas.1404247111]

¹ Ian B. Hutchinson, ²John Parnell, ^1,3Howell G.M. Edwards, ⁴Jan Jehlick, ⁵Craig P. Marshall, ¹Liam V. Harris, ¹Richard Ingley

¹ Department of Physics and Astronomy, Space Research Centre, University of Leicester, University Road, Leicester LE1 7RH, UK
² Department of Geology & Petroleum Geology, University of Aberdeen, King’s College, Aberdeen AB24 3UE, UK
³ Centre for Astrobiology and Extremophiles Research, School of Life Sciences, University of Bradford, Bradford BD7 1DP, UK
⁴ Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Sciences, Charles University, Albertov 6, 12843 Prague 2, Czech Republic
⁵ Department of Geology, University of Kansas, 1475 Jayhawk Blvd., Lawrence, KS 66045, US

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Reference
Hutchinson IB, Parnell J, Edwards HGM, Jehlick J, Marshall CP, Harris LV, Ingley R (2014) Potential for analysis of carbonaceous matter on Mars using Raman spectroscopy. Planetary and Space Science (in Press)
Link to Article [DOI: 10.1016/j.pss.2014.07.006]

¹J. S. Greaves1 et al. (>10)*
*Find the extensive, full author and affiliation list on the publishers website.
¹ SUPA, Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK

Far-infrared Herschel images of the epsilon Eridani system, seen at a fifth of the Sun’s present age, resolve two belts of debris emission. Fits to the 160 μm PACS image yield radial spans for these belts of 12-16 and 54-68 AU. The south end of the outer belt is ≈10% brighter than the north end in the PACS+SPIRE images at 160, 250, and 350 μm, indicating a pericenter glow attributable to a planet “c.” From this asymmetry and an upper bound on the offset of the belt center, this second planet should be mildly eccentric (ec ≈ 0.03-0.3). Compared to the asteroid and Kuiper Belts of the young Sun, the epsilon Eri belts are intermediate in brightness and more similar to each other, with up to 20 km sized collisional fragments in the inner belt totaling ≈5% of an Earth mass. This reservoir may feed the hot dust close to the star and could send many impactors through the Habitable Zone, especially if it is being perturbed by the suspected planet epsilon Eri b, at semi-major axis ≈3 AU

Reference
Greaves JS et al. (>10) (2014) Extreme Conditions in a Close Analog to the Young Solar System: Herschel Observations of Eridani. The Astrophysical Journal Letter, 791 L11

Link to Article [doi:10.1088/2041-8205/791/1/L11]

^1,2Amy L. Fagan, ^1,2,3Katherine H. Joy, ^1,2Donald D. Bogard, ^1,2David A. Kring

¹ Center for Lunar Science and Exploration, Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX, 77058, USA
² NASA Lunar Science Institute, Moffett Field, CA, USA
³ School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Williamson Building, Oxford Road, Manchester, M13 9PL, UK

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Reference
Fagan AL, Joy KH, Bogard DD, Kring DA (2014) Ages of Globally Distributed Lunar Paleoregoliths and Soils from 3.9 Ga to the Present. Earth, Moon, and Planets 112, 1-4, 59-71

Link to Article [10.1007/s11038-014-9437-7]

¹N.A. Starkey, ¹I.A. Franchi, ² M.R. Lee

¹ Planetary and Space Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA
² School of Geographical and Earth Sciences, University of Glasgow, Gregory Building, Lilybank Gardens, Glasgow G12 8QQ, UK

Two interplanetary dust particles (IDPs) investigated by NanoSIMS reveal diverse oxygen isotope compositions at the micrometer-scale. The oxygen isotope values recorded at different locations across the single IDP fragments cover a wider range than the bulk values available from all IDPs and bulk meteorites measured to date. Measurement of H, C, and N isotopes by NanoSIMS, and the use of scanning and transmission electron microscopy (SEM and TEM) to determine elemental compositions and textural information allows for a better understanding of the lithologies and organic signatures associated with the oxygen isotope features.

IDP Balmoral, a ∼15μm-sized fragment with a chondritic porous (CP) -IDP-like texture, contains a region a few micrometers in size characterised by 16O-depleted isotope signatures in the range δ17O, δ18O = +80 to +200 ‰. The remainder of the fragment has a more 16O-rich composition (δ18O = 0-20 ‰), similar to many other IDPs and bulk meteorites. Other than in discrete pre-solar grains, such extreme 16O-depletions have only been observed previously in rare components within the matrix of the Acfer 094 meteorite. However, TEM imaging and FeO/MgO/Si ion ratios indicate that the 16O-depleted regions in Balmoral did not form by the same mechanism as that proposed for the 16O-depleted phases in Acfer 094. As the level of 16O depletion is consistent with that expected from isotope selective self-shielding, it is likely that the 16O-depleted reservoir was located close to that where oxygen self-shielding effects were most pronounced (i.e. the outer solar nebula or even interstellar medium).

Individual regions within IDP Lumley cover a range in δ18O from -30 to +19 ‰, with the oxygen isotope values broadly co-varying with δD, δ13C, δ15N, light-element ratios and texture. The relationships observed in Lumley indicate that the parent body incorporated material at the micrometer-scale from discrete diverse isotopic reservoirs, some of which are represented by inner Solar System material but others which must have formed in the outer Solar System.

The IDP fragments support a model whereby primary dust from the early solar nebula initially formed a variety of reservoirs in the outer solar nebula, with those at lower AU incorporating a higher proportion of inner Solar System chondritic dust than those at larger AU. These reservoirs were subsequently disrupted into micrometer-sized clasts that were re-incorporated into IDP parent bodies, presumably at large AU. These results reveal that any models accounting for mixing processes in the early solar nebula must also account for the presence of an extremely 16O-depleted reservoir in the comet-forming region.

Reference
Starkey NA, Franchi IA, Lee MR (2014) Isotopic diversity in interplanetary dust particles and preservation of extreme 16O-depletion. Geochimica et Cosmochimica Acta (in Press)
Link to Article [DOI: 10.1016/j.gca.2014.07.011]

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